Partially opening door latch



Oct. 11, 1966 H. D. MARCH PARTIALLY OPENING DOOR LATCH Filed Sept. 8, 1964 2 Sheets-Sheet l INVENTOR HARRY 0. MARCH @Zd'L-W ATTORNEYS Oct. 11, 1966 H. D. MARCH PARTIALLY OPENING DOOR LATCH 2 Sheets-Sheet 2 Filed Sept. 8, 1964 /N VEN TOP HARRY 0. MARCH A T TOP/V5 VS United States Patent 3,278,213 PARTHALLY OFENIN G DOOR LATCH Harry ll). March, 1365 Altschule Ave. Menlo Park, Calif. Filed Sept. 8, 1964, Ser. No. 394,938 10 filaims. (Cl. 292-263) This invention relates to door latches, and more particularly to door latches which permit partial opening of the door while the latch is engaged.

As is well known, the usual type of door latch which permits partial opening of the door is called a night latch which has a chain member attached to either a door or the door-jamb, and a cooperating slotted member attached to the other member. The usual type of night latch comprising a chain sulfers from the disadvantage that the chain swings freely and contacts the surface of the door and the door-jamb. The frictional contact of the swinging chain can eventually result in semicircular scrape marks on a door surface, leading to an unsightly appearance. The frictional contact with painted surfaces chips paint and may damage the surface of the door when the door is opened while the chain is engaged with the slotted member. Moreover, the frictional contact with the door and door-jamb surfaces results in scraping the finish from the chain and slot members as well. Therefore, the appearance of the door area surrounding the door latch may become so degraded that the frequent repair or painting may be necessary. The conventional night latch chain also suffers from the disadvantage that its strength is limited by the weakest link in the chain and in that it becomes unduly bulky when an attempt is made to greatly increase its strength.

In general it is an object of the present invention to provide a door latch having great strength.

A further object of the invention is to provide a door latch of the above character in which the forces acting on all of the principal components are in shear during an attempt to open the door.

A further object of the invention is to provide a door latch of the above character which can be readily latched and unlatched.

A further object of the invention is to provide a door latch of the above character which permits partial opening of the door while still preventing disengagement of the door latch from the outside.

A further object of the invention is to provide a door latch of the above character which can only be unlocked when the door is closed.

A further object of the invention is to provide a door latch of the above character which can be readily manufactured and installed.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a front elevational view of one latch member of the door latch attached to the inner face of a door.

FIGURE 2 is an isometric view of a different latch member forming a part of the door-jamb.

FIGURE 3 is an isometric view of the latch member shown in FIGURE 1 but moved to a position in which it can be secured to the latch member on the door-jamb.

FIGURE 4 is a cross sectional view taken along the lines 4-4 of FIGURE 1.

FIGURE 5 is an isometric view of the latch members in unlatched positions with the door closed.

FIGURE 6 is an isometric view of the latch members being latched together while the door is closed.

FIGURE 7 is an isometric view of the latch members latched together and resting in their normal positions with the door closed.

FIGURE 8 is an isometric view of the latch members latched together with the door opened as far as permitted by the door latch.

In general, the door latch incorporating my invention is adapted for use with a hingedly mounted door movable'between open and closed positions in a door-jamb. The door latch is mounted on the inner face of the door to prevent it from being opened beyond a predetermined distance. The latch comprises two arms, one of which is adapted to be pivotally mounted on the door and the other of which is adapted to be pivotally mounted on the door-jamb. The two arms are adapted to move in substantially adjacent parallel planes, and means for releasably securing the arms to each other.

As shown in the drawings, the door latch incorporating the present invention consists of a first member or arm 11 and a second member or arm 12. One of the arms is attached to the door 13, and the other arm is attached to the do'or-jamb 14. The door 13 is adapted to move between open and closed positions with respect to the door-jamb 14 and is mounted on the door-jamb by suitable means, such as hinges (not shown). As shown in FIGURE 2, arm 12 is pivotally mounted on door-jarnb 14 for movement in a plane generally perpendicular to the wall in which the door-jamb is located, Similarly, arm 11 is pivotally mounted on the door 13 for movement in a plane substantially perpendicular to the plane of. the door. Thus, when the door is closed, the arms 11 and 12 lie in substantially adjacent parallel planes (see FIGURES 6 and 7). The arms may be of any suitable strong material, as for example steel, and may take any appropriate shape, for instance elongate, as shown.

Cooperative means carried by the first and second arms is provided for releasably interconnecting the first and second arms. Such as shown in the drawings can consist of a pin 16 attached to one of the arms, and a slot 34 in the other of the arms. FIGURE 3 indicates the pin 16 formed in arm 11 and FIGURE 2 illustrates slot 34 formed in arm 12, although, of course, the slot and pin functions are interchangeable. That is, the slot could be formed in the arm attached to the door, and the pin could be attached to the arm attached to the door-jamb. The pin 16 fits in the slot 34 when the door is closed in the door-jam-b. When attached, the pin and slot connection prevents the door from opening beyond a predetermined distance.

Suitable means is employed for attaching the arms to the door and the door-jamb. Arm 12a is pivoted on a pin 17 which attaches the arm to plate 18. Plate 18 in turn is attached to the door-jamb 14 by appropriate means, as for example screw 19. The arm 12 is provided with an enlarged end portion 12a which is adapted to cover the means for securing the plate to the door-jamb. The enlarged end portion 12a prevents interference with the mounting means 19 by those outside the door.

Suitable means may be employed to attach the arm 11 to the door 13. The means illustrated in the drawings consists of a hinge 21, the flange of which is attached to the door 13. The strap 22 of the hinge is attached to arm 11 by means of pin 23. Pin 23 permits rotation of the arm 11. Hinge strap 22 swings from a position flat against the door to a position perpendicular to the door as illustrated in the dotted lines of FIGURE 4. The hinge member prevents the arm 11 from extending any substantial distance into the room to provide a safety hazard. If desired, fixed means may be employed to permit arm 11 to swing in a plane substantially parallel and adjacent to the plane in which arm 12 moves.

As best seen in FIGURES 1 and 3, pin 16 has an enlarged head portion, and a narrower body portion 24.

Body portion 24 is oblong in cross section. The slot 34 formed in arm 12 (FIGURE 2) is contour in shape, with the upper portion being larger than the lower portion. The enlarged head of pin 16 is adapted to fit in the enlarged upper portion of slot 34 in arm 12, and the body portion 24 is adapted to engage the lower end of the slot 34. When the pin is engaged at the lower portion of slot 34 the enlarged head of the pin 16 prevents disengagement of the arms. The preferred oblong cross section of the body portion 24 of the pin 16 results in increased strength of the pin 16, and provides a firm seat throughout a substantial portion of the slot 34 when the arms are interconnected together.

As illustrated in the drawings, arm 11 is substantially shorter than arm 12. Arm 11 is thus incapable of swinging outside the door 13 to such an extent that the pin may be disengaged from the slot by one outside the door. The length of arm 12 determines the maximum distance the door may be opened when the arms are attached.

Suitable means are employed to prevent the arms from being rotated to such an extent that the pin and slot may be disengaged by one outside the door. The oblong body portion 24 of pin 16 will not rotate beyond a predetermined angle in the lower portion of slot 34. In addition, abutment means 26 is attached to the hinge strap 22 to prevent rotation of arm 11 beyond a predetermined angle.

The operation of the latching device is illustrated in FIGURES 5 through 8. In FIGURE 5, the normal opened position of the device is illustrated. The hinge strap 22 is swung back so that it lies fiat against the door 13 and arm 11 does not protrude therefrom. Similarly, arm 12 is in a lowered position and does not extend into the room to provide an obstruction. As is apparent from FIGURE 5, the device provides a flat and relatively inconspicuous appearance.

When it is desired to engage the door latch the position illustrated in FIGURE 6 is used. Thus, the hinge 22 is swung open so that the arm 11 is in a plane parallel and adjacent to that of arm 12. Arms 11 and 12 are then swung out into the room to a point where they may be engaged by the pin 16 in slot 34. As noted above, the enlarged head of pin 16 will fit only into the enlarged upper portion of the slot 34. After engagement, the smaller body portion 24 of the pin 16 is movable within the upper and lower portions of the slot 34.

After the arms are attached, the arms may be lowered into the position shown in FIGURE 7. Arms 11 and 12 are still attached by means of the pin 16 and slot 34. This is a normal night latch position, in which the latch provides an extra lock, in addition to the usual door lock present.

Should the door be desired to be opened partially, as for example viewing visitors, the position shown in FIG- URE 8 may be taken. In this position, the arm 11 is r-otated in a direction outside the room, and the arm 12 is rotated in a direction inside the room. Further rotation of the arms is prevented by two factors: First, the abutment means 26 on hinge strap 22 prevents the arm 11 from rotating beyond a predetermined angle. Secondly, the oblong cross sectional shape of the body portion 24 of the pin 16 prevents the rotation of the pin in the slot 34 beyond a predetermined angle. Thus, the body portion 24 seats firmly at the lower portion of the slot 34, and may not be rotated further than the position shown in FIGURE 8. The short arm 11 does not extend into the space between the door and the door-jamb. This prevents tampering with the pin connecting the arms 11 and 12 together by one outside the door. On the other hand, arm 12 is relatively long to provide a maximum space when the door is in the partially opened position of FIGURE 8. I have found it helpful to employ a slight offset in arm 12 to keep the lower end thereof away from frictional contact with door-jamb 14.

It will be apparent that the tamper-proof integrity of the device is quite high. In the embodiment shown, no access to the mounting screws 19 of the arm 12 is available. Access to the mounting means of arm 11 is difficult, if not impossible. The arms may not be engaged or disengaged except when the door is closed. The arms may not be swung to a position at which the pin may be disengaged from the slots, because of the abutment means 26 on the hinge 22. The filled portion 24 of the pin 16, providing an oblong cross section, prevents rotation of the pin in the slot beyond a predetermined angle.

The door latch is extremely strong. Unlike the normal night latch chain in which the expansion of the chain may force links to open, the forces acting on the parts are in shear or in compression. Thus, the long mount screw for attaching the arm 12 to the door-jamb is loaded in shear. This is the main attach point for the plate on which the long arm 12 is pivoted. Similarly, the load on pivot pin 17 is also in shear. The load on the center pivot pin 16 is in shear. When the door is being forced open against the restraining action of the door latch, the two hinged sections are caused to be forced into a tighter bond. The load on the two hinged sections is in compression. I prefer to employ a high strength steel for all of the pins, for example Monel steel. Of course, any high strength material may be used.

It will be apparent from the foregoing that I have provided a simple type of door latch in which a pair of arms are placed in planes which are substantially adjacent and parallel, are fastened together with a pin, and the pins are rotatable in their respective planes to provide a predetermined amount of opening the door, without danger of tampering.

I claim:

1. In a door latch for use with a door hingedly mounted in a door-jamb for preventing the door from being opened beyond a predetermined distance, a first arm adapted to be pivotally mounted on said door, a second arm adapted to be pivotally mounted on said jamb, said first and second arms being movable to a position lying in substantially adjacent parallel planes, cooperative releasable pivot means carried by the arms releasably interconnecting the arms so that said first and second arms are locked together to prevent said door from being opened beyond a predetermined distance, said cooperative means also permitting said door to be moved to a closed position while locked, said cooperative means forming rigid abutment means releasable when said arms attain a relative relationship corresponding to the substantially closed door position.

2. In a door latch for use with a door hingedly mounted in a door-jamb for preventing the door from being opened beyond a predetermined distance, a first arm adapted to be pivotally mounted on said door, means for pivotally mounting said first arm, a second arm adapted to be pivotally mounted on said jamb, means for pivotally mounting the second arm on the jamb, said first and second arms being movable to positions lying in substantially adjacent parallel planes, a pin formed with an enlarged head portion and a narrower body portion rigidly carried by one of said arms, a slot formed in the other of said arms, said slot being formed with an enlarged portion corresponding in size to said enlarged head portion of the pin and a narrower slot portion corresponding to said narrower body portion of the pin so that said first and second arms may be engaged by inserting said pin in said slot to lock together the arms and prevent said door from being opened beyond a predetermined distance, said pin and slot also permitting said door to be moved to a closed position.

3. A door latch as in claim 1 wherein said first arm is mounted at one end thereof on the inner face of the door and is relatively short so that said arm is incapable of swinging outside the door to such an extent as to permit disengagement of the pin and slot by one outside the door.

4. A door latch as in claim 2 wherein said second arm is adapted to be pivotally mounted at one end thereof to said door-jamb, said end bearing an enlarged portion of said arm capable of blocking access to its mounting means while said pin and slot are engaged.

5. In a door latch for use with a door hingedly mounted in a door-jamb for preventing the door from being opened beyond a predetermined distance, a first arm pivotally mounted at one end thereof on said door, pivot means adapted to permit said arm to swing in a plane substantially perpendicular to the plane of said door, a second arm pivotally mounted at one end thereof on said jamb, pivot means on said jamb for attaching said second arm to said jamb and permitting the arm to swing in a plane substantially perpendicular to the plane of said door, said planes in which said first arm and said second arm swing being substantially adjacent parallel planes, a headed pin carried at the other end of said first arm, a slot formed in the other end of said second arm, said pin and said slot corresponding in size so that said arms may be locked together to prevent said door from being opened beyond a predetermined distance and being releasable when said door is in a substantially closed position.

6. A door latch as in claim 5 wherein said slot is formed with a larger portion and a smaller portion, said larger portion being adapted to receive said pin only when said door is closed, said smaller portion of said slot adapted to permit movement of said arms in said planes without disengagement of said pin from said slot.

7. A door latch as in claim 6 wherein said pin carried at the end of said first arm is formed with an enlarged head portion adapted to correspond to the larger slot portion so that the pin will engage or disengage the slot only when said door is closed, and a smaller body portion on said pin adapted to slide freely in said smaller portion of said slot.

8. In a door latch for use with a door hingedly mounted in a door-jamb for preventing the door from being opened beyond a predetermined distance, a first arm adapted to be pivotally mounted on said door, a second arm adapted to be pivotally mounted on said jamb, said first and second arm being movable to positions lying in substantially adjacent parallel planes, a pin rigidly carried by one of said arms, said pin having an enlarged head portion, and a narrower body section which is oblong in cross section, a slot formed in the other of said arms, said slot having an enlarged portion adapted to receive the enlarged head portion of said pin when said door is in the substantially closed position, and said slot having a narrower portion into which said narrower body portion of said pin fits, said oblong cross section of said body portion being adapted to prevent rotation of said pin beyond a predetermined amount, said pin and slot also permitting said door to be moved to a closed position.

9. A door latch as in claim 8 wherein said first arm is adapted to be pivotally mounted on a hinge member attached to the door so that the first arm m-ay swing fiat against the door.

10. A door latch as in claim 8 wherein said pivot means for mounting said first arm carries an abutment means, said abutment means adapted to be engaged by the first arm to prevent pivotal movement of the arm beyond a predetermined angle.

References Cited by the Examiner UNITED STATES PATENTS 251,732 1/1882 Phillips 292-268 611,291 9/ 1898 Stebbins 292-263 1,447,846 3/1923 Hill 292-262 X 2,562,916 8/1951 Hoffman 292-265 2,650,847 9/1953 Olson 292-265 2,745,692 5/1956 Persson 292-263 FOREIGN PATENTS 325,725 2/ 1930 Great Britain.

EDWARD C. ALLEN, Primary Examiner.

R. E. MOORE, Assistant Examiner 

1. IN A DOOR LATCH FOR USE WITH A DOOR HINDEDLY MOUNTED IN A DOOR-JAMB FOR PREVENTING THE DOOR FROM BEING OPEN BEYOND A PREDETERMINED DISTANCE, A FIRST ARM ADAPTED TO BE PIVOTALLY MOUNTED ON SAID DOOR, A SECOND ARM ADAPTED TO BE PIVOTALLY MOUNTED ON SAID JAMB, SAID FIRST AND SECOND ARMS BEING MOVABLE TO A PISTON LYING IN SUBSTANTIALLY ADJACENT PARALLEL PLANES, COOPERATIVE RELEASABLE PIVOT MEANS CARRIED BY THE ARMS RELEASABLY INTERCONNECTING THE ARMS SO THAT SIAD FIRST AND SECOND ARMS ARE LOCKED TOGETHER TO PREVENT SAID DOOR FROM BEING OPENED BEYOND A PREDETERMINED DISTANCE, SAID COOPERATIVE MEANS ALSO PERMITTING SAID DOOR TO BE MOVED TO A CLOSED POSITION WHILE LOCKED, SA ID COOPERATIVE MEANS FORMING RIGID ABUTMENT MEANS RELEASABLE WHEN SAID ARMS ATTAIN A RELATIVE RELATIONSHIP CORRESPONDING TO THE SUBSTANTIALLY CLOSED DOOR POSITION. 